Hi kaliope, I can imagine that seeing her photo also gave you a feeling of loss, of emptiness, senselessness, and a hole where she was/where she should be now???
And maybe things could have/should have been different for her (and for you!!) but as much as we'd like to/wish to there's no turning back the clock and even if it was possible there's nothing to say where that would lead to instead.
So perhaps instead you could try right now to honoring her for the life she did lead?? She must have been incredibly strong to have gone through all she went through, and she must have had a lot of fight in her to make it as far as she did???
And you know seeing the "bigger picture" can sometimes cost you the price of seeing/feeling some of the intricacies of her/her life.........the intricacies which are really precious, really special.
Maybe there are memories you can hold onto when she smiled, when she made you smile, moments you shared, times you could be there for her, times you felt real close to her, times she lifted you. I understand there might not be that many, but they say just as much about a person and the life they had than anything else.
So maybe try not to feel sad for her........I'd say that you probably more have the right to be proud of her, to have had her as your sister.
And as for not always being there for her, ignoring calls..........well I'm sure you had reasons for that.........maybe you were having a really hard time yourself, maybe you found that connection hard or distressing, maybe some things were triggering for you??? Either way you did what you were able to do, you did care and please don't assume she didn't know that. There's nothing to say she didn't. And she may well have clearly understood how hard it might have been for you, after the things you'd gone through together, after knowing how hard things could be.
And as for her being gone.........well you still keep her inside you/in your heart, you still keep her/your memories, right?? You know she's probably closer to you than you feel right now with all that you've still got left of her.
And remember that strength she had, remember the positive and inspiring things about her. Allow those gifts she gave you from knowing her to give you some of the warmth, comfort, positive affirmation...........you might need right now and whenever.

Alison